Animation involves the generation of a series of still images that, when played back in quick succession, appear as continuously moving. In computer animation, a rendering process is used to generate a two-dimensional image of a three-dimensional scene from a given viewpoint. Animated sequences can be created by rendering a sequence of the rendered images of a scene as a scene is gradually changed over time. A great deal of effort has been devoted to making the rendered images and the resultant animation realistic.
In some instances, the animation of objects may be independent of the environment surrounding the objects being animated during an animation process. However, in certain situations, the animation of the object may depend on other objects in the environment, other objects it is connected to, or the animation of several parts of the object, in order to be positioned appropriately to increase the realism of the animation. For example, the animation of a character with appendages such as an arm on a table can include controlled animation of a shoulder, elbow, wrist, and fingers on the table surface such that when animated a physically realistic look is provided, e.g., not penetrating the table surface or having an awkward, unnatural angle in the elbow. The character also can react to changes in its environment or appendages. For example, the arm on the table can have a different position when the controlled character is sitting down compared to standing up. In a first state the character may be resting the arm on the table while sitting down in a chair at the table. Then, in a second state when the character stands up from the chair, the arm's position can change accordingly but the hand, or parts of the arm, may remain resting on the table.
Typically, the associated animation of objects or parts of objects is handled manually by the animator or user. For example, to move the character from a sitting position to a standing position, the animator manually and individually adjusts the movement and position of every component of the arm (including the shoulder, elbow, hand, and fingers) relative to the table surface and to the character's body such that the movement of the entire arm and character remains as realistic as possible. Such manual setting of objects or parts of objects can be tedious and time consuming for an animator. Therefore it is desirable to provide improved techniques that overcome the above and other problems.